Blizzard has introduced the Curse of Naxxramas, the first major expansion for Hearthstone, its collectible card game on iPad, PC and Mac.

The free-to-play expansion bolsters the single player mode of the game, introducing players to the five wings of Naxxramas, an ancient necropolis ruled by the archlich Kel'Thuzad.

In practical terms, that means that players duel against several new AI decks and heroes, winning rewards such as new legendary cards, class-specific spells and minions, and a unique set of art for the backs of their decks.

Released on Wednesday, the first "wing" of the expansion is free to play for the first month, and includes three new opponents: the Spider Lord Anub'Rekhan, Grand Widow Faerlina, and the wing boss Maexxna the spider queen. Beating each of them grants the player a new pair of cards, and winning against all three unlocks Maexxna herself as a legendary card.

Beating the three bosses also unlocks two of the expansion's class challenges, for Rogue and Druid, which give players pre-made decks and challenge them to beat an opponent tailored to exploit their strengths and weaknesses, as well as a heroic mode which cranks the difficult up to ludicrous levels.

Over the next five weeks, the other four wings will be opened up to the public, and players can buy entry for real money or in-game gold. A single wing will cost £4.99 or 700 gold, while there are discounts for buying multiple wings at once. Once the launch month ends, the overall price of all five wings will max out at £17.49.

First thoughts

The first pass through the dungeon won't keep many players occupied for that long. With a moderately rounded deck, it's perfectly possible to beat each of the bosses on the first try, and there's little reason to replay them once you're done.

But the class challenge and heroic modes offer more prospects for long-term fun. The pre-made decks of the former are worth playing with several times just to get a sense of the sort of deck-building enabled by the new cards offered in the expansion.

As for the latter … look, you aren't going to beat it for a while. One of the bosses in heroic mode has a hero power that lets them return two of your cards to your hand. It costs zero mana. It will annihilate you.

But in the long term, the effect of Naxxramas is likely to be in the cards it adds to the pool. There's a strong theme of death running throughout, with most of the new minions having "deathrattle" effects, which fire when they're killed, and by the end of the expansion, there will be a further six legendary cards available to all.

Moreover, the expansion effectively changes the model of the game's new cards from that of a collectible card game – where players buy packs of five random cards out of a total pool of 250 – to something more like a "Living Card Game", of the sort used in games such as the Game of Thrones and Star Wars card games. Once Naxxramas has been out for a while, every player will have access to the same pool of 30 cards, with a fair few extremely strong contenders. That could have the effect of dampening some of the game's more unsavoury pay-to-win elements (where those players who have invested hundreds of pounds in new cards wind up with a hefty advantage in PvP play).

The big downside of the expansion? It makes the unnecessary restriction against offline play much more painful. Offering strong, fun AI opponents to play against should make the game the perfect companion for flight, or a quick journey underground. Instead, it just makes Blizzard feel a bit money-grubbing.